1. Field of the Invention
The present invention relates to a one-liquid-type epoxy-resin composition. More precisely, it relates to a one-liquid-type epoxy-resin composition with excellent storage stability, which can be rapidly cured under heat to give a cured resin with excellent properties.
2. Description of the Background
Epoxy resins are cured with an acid-anhydride-type hardener, a polyamine-type hardener, or the like to give cured resins having excellent electrical, mechanical and chemical properties. These resins are used in the various fields of electric insulating materials, the preparation of various shaped products, adhesives, coating compositions, and the like. Epoxy resin compositions which are generally used at present are of a two-component type comprising a base component consisting essentially of an epoxy resin and a hardener component consisting essentially of an acid anhydride, a polyamine compound, or the like. Two-component-type epoxy-resin compositions can be cured at room temperature or at low temperatures, while, on the other hand, the pot life of a resin mixture which is prepared when mixing the two components is limited. Therefore, workers must prepare the compositions freshly each time they are needed. The preparation of the compositions requires troublesome processing which requires precision in weighing the components and mixing and stirring the ingredients. Consequently, the workability of the compositions is often poor. In addition, such operations often cause errors. Moreover, since the remainder of the composition cannot be stored as it is, it must be discarded, which represents a waste of material. Thus, compositions of this type have various disadvantages.
In order to overcome these drawbacks, some one-liquid type epoxy-resin compositions have been proposed in the past. For instance, one proposed epoxy-resin composition contains a latent hardener such as dicyandiamides, dibasic acid dihydrazides, boron trifluoride-amine adducts, guanamines, melamines, and the like. However, dicyandiamides, dibasic acid dihydrazides and guanamines are defective in that they require high temperatures of 150.degree. C. or higher in order to cure, as well as long periods of time for the epoxy resins to cure. However, the compositions have good storage stability. Boron trifluoride-amine adducts can not be said to be practically useful, because they have high moisture absorptability and because they have a negative influence on the properties of the cured resins. Further, they corrode metals. In view of the current state-of-the-art as described above, it has been desirable to provide epoxy-resin compositions that have both good storage stability at room temperature and rapid curability and which can be cured to give cured products having excellent properties.
In order to overcome the above-mentioned problems, methods have been proposed for using, as the hardener, a so-called solid-dispersing, amine-adduct-type latent hardener. Such a hardener can be obtained, for example, by reacting various amine compounds with epoxy compounds, or the like by an addition reaction. For example, such a hardener can be obtained by reacting a dialkylamine and an epoxy resin, as proposed in Japanese Patent Laid-Open Nos. 56-155222 and 57-100127. Another method of preparing the hardener is melt-masking a reaction product obtained from an N,N-dialkylaminoalkylamine and an epoxy resin with a polyphenol compound as proposed in Japanese Patent Laid-Open No. 61-228018. Still another method of preparing the hardener is by making a powdery amine having a tertiary amino group kept in contact with a polyisocyanate as proposed in Japanese Patent Publication No. 3-70736. Yet another method of preparing the hardener is by reacting an N,N-dialkylaminoalkylamine, a cyclic amine having one or two active hydrogens in the molecule and a diisocyanate in the presence of an epoxy resin as the third component, having two or more epoxy groups in one molecule as proposed in Japanese Patent Laid-Open No. 3-296525. Another method of preparing the hardener is by reacting a phenol or alcohol having a tertiary amino group and an epoxy resin as proposed in Japanese Patent Publication No. 1-60164. However, the solid-dispersing latent hardeners obtained by the above-mentioned methods are still not satisfactory for practical use, even though they are curable at low temperature and have storage stability. In addition, their storage stability is noticeably decreased by the epoxy resins to be used or by the presence of additives such as diluents and the like which are added thereto. Thus, these hardeners are not always satisfactory.
In order to further overcome these drawbacks, a composition has been proposed which contains a solid-dispersing latent hardener, of which the surfaces of the particles have been treated with an aluminum alcoholate or a chelated aluminum compound (Japanese Patent Laid-Open No. 63-223027). However, this compound does not have acceptable storage stability.
Given this situation, it has been highly desirable to provide an easy-to-produce, one-liquid-type epoxy-resin composition which has good storage stability and which is rapidly curable at low temperature, without being influenced by the epoxy resins used and by additives such as diluents, and the like which are added thereto, and which can be cured to give cured products having excellent properties.